FLINT TOWNSHIP, MI -- Fuel economy is becoming an industry standard for automakers as the price at the pump trends upward and the federal government continues pressure for a greater reduction in emissions.

General Motors Co. has now unveiled a new welding technology that will increase the amount of aluminum used in its vehicles to reduce weight and improve fuel efficiency.

Invented by David Sigler, a technical fellow with GM, the process is called resistance spot welding and was unveiled Tuesday morning at the Flint Metal Center in Flint Township.

The technology is now being used for the hood of the Cadillac CTS-V and the lift gate for the hybrid version of the Chevrolet Tahoe and GMC Yukon. It will be used more extensively starting next year.

“We are going to be implementing it across the board,” said Eric Cuddeback, a manufacturing engineer with the Flint Metal Center. “We are looking at aluminum more and more because of the weight savings. We are looking at other hoods and also doors and different lift gates.”

Spot welding is a process of joining two pieces of metal using electric current. The electricity is run through two opposing electrode pincers to compress and fuse the pieces.

The process was better suited for steel as opposed to aluminum because it wouldn’t break the surface.

David SiglerRyan Garza | MLive

Aluminum “is very difficult to weld because you have an oxide on the surface,” Sigler said. “It’s almost like a thin sheet of glass on the surface you have to break down in order to get the current weld to flow through the sheets.

“We tried some different ideas on how to do that. We sand-blasted an electrode in order to break through the surface, but that didn’t work well in the plant setting.”

Michael Karagoulis, a master mechanic of welding development for GM, has been working in the manufacturing engineering department as a welding engineer with welding caps.

David had come to him about the idea of resistance spot welding, which led to a welding cap being developed with rings on the tip.

“Dave needed a completely different geometry than we are used to with steel, but we had already worked on the cutting technology to maintain the shape of the caps so he asked if we could do this with a new geometry for aluminum and this was the result,” said Karagoulis.

Prior to the new process, self-piercing rivets have been used to join aluminum body parts like hoods, liftgates and doors.

“As we look at implementing more and more aluminum in the future, we can use this to expand the use of spot welding to these other applications," said Blair Carlson, lab group manager for light-weight material processing for GM. “A lot of what you see is maybe thin gauge sheet, but what you’ll find next year as we launch our vehicles, it’s going to go to sheet, extrusions and castings and that’s really where a breakthrough technology shines.

“Production today is mostly set up around spot welding steel, so as we transition to aluminum it’s less disturbance in the plant, less disturbance with the people in production to transition from steel spot welding to aluminum welding.”

Aluminum can be as much as 30 to 40 percent lighter than steel in some parts, which has a dramatic impact on weight and fuel economy, said Cuddeback, standing next to a Cadillac hood that was being welded.

“By going to aluminum, this hood weighs about 20-some pounds and before they were close to 60,” he said. “So there is a big difference in the weight.”